BEIJING, Sept. 15 (AFP) - China has locked down a city on the border with Myanmar and will launch a mass coronavirus testing programme, officials said Tuesday (Sep 15), after a handful of infections were detected there.

The three cases were found in the city of Ruili in western Yunnan province, a major land border crossing point with neighbouring Myanmar.

City officials said in a statement Tuesday that residents were being told to stay home and people had been forbidden from entering or leaving the city from Monday evening.

They said every resident would be tested for the virus in Ruili, which is home to more than 210,000 people.

Businesses have been closed except for supermarkets, pharmacies and food markets.

The infections were brought in from Myanmar and Chinese authorities would "crack down on illegal immigrants", the officials said.

Ruili is separated by a shallow river from the border town of Muse, Myanmar's main gateway to China known for sleazy streets, weapons, casinos and drugs.

Yang Bianqiang, vice mayor of Ruili, told a press conference on Monday that the city would repatriate those who cannot verify their time of arrival into China, "have no fixed residence and have no fixed place to work".

China has largely controlled the spread of the virus through a series of travel restrictions and strict lockdowns, starting with the central city of Wuhan were the virus first emerged late last year.

However, there have been a number of localised outbreaks in recent months including in the capital Beijing.

The country's borders remain closed to most foreigners, and the majority of infections in recent months have been from returning overseas nationals.

Seven other cases were reported around China on Tuesday - all brought in from other countries, the National Health Commission said.

Myanmar is a vital piece of China's Belt and Road Initiative - Chinese President Xi Jinping's US$1 trillion vision for maritime, rail and road projects across Asia, Africa and Europe - including a proposed US$8.9 billion high-speed rail link from Yunnan to Myanmar's west coast.